enum Weekdays {
   Sunday, Monday, Tuesday, Wednesday, 
   Thursday, Friday, Saturday
};
Weekdays Day;
if (Day == Tuesday || Day == Wednesday 
    || Day == Friday) {
  DoThisThreeTimesAWeek();
}

enum Weekdays {
  Sunday = 0x01, Monday = 0x02, Tuesday = 0x04, 
  Wednesday = 0x08, Thursday = 0x10, 
  Friday = 0x20, Saturday = 0x40
};
Weekdays Day;
if (Day & (Tuesday | Wednesday | Friday)) {
  DoThisThreeTimesAWeek();
}